Process of preparing pyridine and 3-picoline



- 2,744,904 PROCESS OF PREPARING PYRIDINE AND, 1 3-PIC0LINE. p

Francis E. Cislak and William R. Wheeler, Indianapolis,; Ind.

No Drawing. Application November 25, 1953,

, Serial No. 394,490

14 Claims. (Cl. 260-290) Our present invention, which is a continuation in part of our co-pendingapplication Serial No. 198,231 filed November 29, 1950, now'abandoned relates to a process of preparing pyridine 'and-3-pico1ine. More specifically, it relates to a process of preparing pyridine and 3-picoline by the interaction of acetylene, ammonia, and methanol.

Pyridine is obtained commercially as a by-product of the coal-tar industry. The manufacture of coal tar, coke, and related products starts with the placing of coal into a chamber and heating it out of contact with air. The coal is thereby decomposed into volatile products and into a non-volatile residue, coke. The volatile products, composed of ,condensable materials and non- 'condensable gases,a're removed from 'theicarbonization chamber and cooled, thereby condensing water and tar. ffThese twosubstances, water andtar, constitute the bulk 'of the eondensable materials evolved during the decomllwith pyridine bases; thepyridines are recovered fromfthis liquor. layneutralizing "with. ammonia gas; from.,the mmonia stilLand separating the thus liberatedcrude pyrid nebasesfrom-the ammonium sulfatesolution- I The'pyridine bases recovered from the cokefoven gases contain a number of individual compounds. y

mercial practice, the crude bases are fractionally distilled into four cuts:

' j Boiling point,' C.

In corn- The 3 -picoline cut isconipos edof abdut equ al parts of .3.- picoline (B. B. 143.9" 0. 4-picoline (13.; P. ,144'.9"'-" "C.)i,. and 2 ,6 -l utidine l (B. P. 143.7? C.).. "Becausefthe boilin g pointsof these three niethylpyridines are so'close together, it is not; possible to separate them from' each other'by fractional di'stillatio'nf The patent literature is "replete with processes for'isolating oneor moreof these.

compounds-from the 3-picoline cut; all are complicated processesand with one exception are 'not' commercially I practicable.

i I Thejianioiivnti'of 'l yridines' thatis normally obtainable as aby-product of coal carbonization is limited." At'the present time this insu'fiicient amount is furthefcurtailed because ofeconomic considerations. The-recovery of -pyridine bases is incidental to the manufacture of: am-

i?'=:monium sulfate; Unless there is a market :for. the amamonium' sulfate, it -.:is,,unprofitable to. recoverapyridineg,

bases from coke oven'gases. Today, some of the largest tarninated by 4-picoline.

methanol with acetylene and ammonia and passthe e- We prepared a gaseous mixture composedfif I I of acetylene, four and one-half parts, of ammonia,

2,744,904 (Patented May 8, 1956 ice producers of coal tar have discontinued recovering pyridine bases'.. 'Themarket for ammonium sulfate has gradually shrunk, until now it is diflicult to sell more than asmall amount of that which is potentially available. With the steady increase in the use of anhydrous ammonia as a fertilizer, it is expected that the demand for ammoniumsulfate will continue to decline. v I I For a number of years the demand for pyridines' has exceeded the supply. If this demand is to be satisfied, it is imperative that a new source of pyridine be foun'df. Many attempts have been made to synthesize pyridine bases. Thus, for example, the U. S. Patent 1,882,158 dated October 11, 1932,.describes a process ofreacting acetylene with ammonia to prepare 2- and 4-r net hyl pyridine as well as poly-methylated pyridines. This prior art patent also discloses a process of preparing quinal dine (which is Z-methylquinoline) '-by. reacting, aniline with acetylene. I i t t. In spite of the years of research that have been. devoted to the study of pyridine synthesis, no one has heretofore developed a commercial process for the simultaneous preparation of pyridine and3-picoline. h Y We have found we can react methanol, acetylene and ammonia to form pyridine and v3-picoline. ,Furthermore, we have foundthat we can so controlthe reaction thatpractically no 2-picoline or 4-picoline is formed- ,In other words, we can make 3-picoline which is uncofn- By our process we can prepare pyridine an economically and in commercial quantities'Qwith ery good yields. A commercial plant utilizing our process .wasput on stream this year.

. .I n carrying out our invention we mix the. va p sultant mixture through a suitable reactor containingi a catalyst. The temperature of the reactor vis maintained :preferably between about 400" C. tthdaboutfSQOf' iC. .We prefer to carry out our. process in acontinuous ner'although that is not necessary. Thereactor used may be of various. types 1 wepreier the fluid catalyst type, similar to thosehorrn y, usedin carrying out cracking operations in the. petroleum; industry. "Such reactors are of tubular form with, suitable connections at entrance and exit. 4 They are provided withmeans for supporting the fluid bed of catalyst, and

I are provided with any convenient means for'heating them.

A highly Satisfactory yn Gamma .gbi itsl j fin s described more fully by mean of h; n w n p cm: ,examplesp' Example 1- i one part of methanol (the parts are by volume).

dine, 2-picoline, and 4-picoline were produced: {The vapors of the unchanged reactants and thereaction products were condensed as theyiemerged from the reactor,

and the condensate was collected in a. suitable. receiver. The pyridine and the picolines were isolated from the condensate by fractional distillation. The pyridine obtainedamounted to about 0.2 pound,for.,.eaqh,=pound of acetylene passed through the reactor.

Example 2 The process of Example 1 was repeated with the exception that the gaseous mixture passed through the reactor was composed of three moles of ammonia and two moles of acetylene. The condensate (reaction prodnot) was'subjected to fractional distillation through the same fractionating column used in Example 1. N pyridine was recovered. 2-picoline was recovered in an amountcorresponding to 34.0% of the reaction product. 4-picoline was recovered in an amount corresponding to 23% of the reaction product; as obtained from the fractionating' column, the 4-picoline had a purity of: more than 97% clearly indicating that no 3-picoline was formed.

Example 3 We prepared a gaseous mixture composed of one mole of acetylene, one mole of ammonia, and three moles of methanol. We passed the mixture of vapors through a fluid catalyst type of reactor inches in diameter and- 20feet-hig'h containing 300 pounds of a fluidized catalytic bed of activated alumina (Alorco H-41) which had "been impregnated with 10% zinc fluoride. The temperature of the reactor was maintained at about 425 C. 'The'gaseous mixture of acetylene, ammonia, and methanol was passed through at a superficial velocity of 1.25 'feet per second. As this mixture of acetylene, am- 'monia, and methanol passed through the reactor, a reaction occurred whereby pyridine and 3-picoline were produced. The vapors of the unchanged reactants and thereactionproducts were condensed as they emerged from the reactor, and the condensate was collected in a suitable receiver.

The'condensate was composed of pyridine compounds and non-basic or neutral compounds. In order to separate these two groups of compounds, the condensate was acidif ed to a pH of 1 with sulfuric acid. The pyridine base compounds present dissolved in the dilute sulfuric acid solution. The non-basic compounds were insoluble and formed a layer on top of the sulfuric acid solution.

These were separated by decantation. The last traces 'ofiion-basic compounds were removed by steaming the sulfuric acid solution. The sulfuric acid solution freed of. non-"basic contaminants was made strongly alkaline (pl-l 12.0) by the addition of sodium hydroxide. Pyriidine bases separated from this strongly alkaline soluti on. "The'y were removed by decantation. Any small amount of pyridines remaining in the alkaline solution were recovered by steam distillation and combinedwith are previously separated bases. 'After drying with flake caustic soda, the pyridine bases were fractionated through a two-inch diameter, 46-foot long fractionating column to'recover pyridine and 3-picoline. The pyridine recovered amounted to 16.5%. The 3-pi-coline amounted to 24.5%; as obtained from the fractionating column, the 3 -pi c.oline had a purity of more than 95%, clearly indicdting that no 4-pico1ine was formed. 2-picoline "was'alsd'recovered, but only in an amount of 2.5%.

Example 4 ilTheaprocess .of Example 3 was repeated with the exception .thatthe gaseous ,mixture passed through the reactor. consisted of one mole of acetylene, one mole of ammonia, and two moles of-methanol. vbases obtained were subjected to fractional distillation The pyridine throughlthe same fractionating column used in Example 3 'The pyridine recovered amounted to 14.5% of the reaction product. The 3-picoline recovered amounted to 22.5%; asQbtained from the fractionating column, ll'11'-3-'piCOliI16 had a purity of more than 95%, clearly "indicating that no 4-piooline was formed. 2-picoline j was recovered inan amount of 4.5%.

q Example 5. p

The-process of Example 3 was repeated with the:

7 amount of 24.5%

The process of Example '3 was repeated with the exception that the gaseous mixture passed through the reactor was composed of one mole of acetylene and one mole of ammonia; no methanol was used. The pyridine bases obtained were subjected to fractional distillation through the same fractionating column used in Example 3. No pyridine was recovered. Z-picoline was recovered in an amount of 32.0%. 4-picoline was re covered in an amount of 28.0%; the 4-picoline had a purity of 93%, clearly indicating that no 3-picoline was formed.

Example 7 The process of Example 3 was repeated with the exception that the gaseous mixture passed through the reactor was composed of two moles acetylene, two moles ammonia, and one mole of methanol. The pyridine bases recovered were subjected to fractional distillation through the same fractionating column used in Example 3. The pyridine recovered amounted to 14.5%. The 3-picoline amounted to 17.5%; the 3-picoline as obtained from the fractionating column had a purity of about 50% indicating that as much 4-pi-coline was formed as there was of 3-picoline. The Z-picoline recovered amounted to 16%.

Example8 The process of Example 3 was 3 repeated with the exception that the gaseous mixture passed through the reactor'was composed of four moles acetylene, four moles ammonia, and one mole of methanol. The pyridine bases recovered were subjected to fractional distillation through the same fractionating column used in Example 3. The pyridine recovered amounted to 11%. The 3-picoline amounted to 17%; as obtained from the fractionating column, the 3-picoline had a purity of about 50%, indicating that 4-picoline was formed in an amount equal to the 3-picoline formed. 2-picoline was recovered in an Example 9 A zinc zeolite catalyst was prepared in the following manner. A four-inch diameter porcelain tube eight feet long was mounted vertically and filled with distilled water. Then 21.75 pounds of Decalso Permutit was slowly added to form an ion exchange bed approximately inches long. A zinc chloride solution (-3.5 pounds of zinc chloride and pounds of water) was flowed downward over the Permutit in order to replace zeolitic sodium by zinc ion. The zeolite was washed with 20 pounds of distilled water, drained, and placed in a drying oven. The zinc zeolite was dried for about 72 hours at 85 C. It was then ground to 65 mesh and finer. (Decalso Permutit is a synthetic sodium-alumino-silicate used for water softening.)

The process of Example 1 was repeated with the ,following exceptions. The zinc zeolite catalyst prepared above was used. The temperature of the reactor was maintained at 425 C. The gaseous mixture passed through the reactor was composedof two molesv ofacet- 'ylene, two moles of ammonia, and one mole of methanol. The. pyridine content of the water-free reaction product was about 29%. The 3-picoline amounted to 24%; as

indicated in Example 4.

obtained from the, fractionating (the 3-picoline had a purity ofabout 50% indicating that 4-picoline' was 3-picoline. The vapors of the unchanged-reactants and T the reaction products were condensed as they emerged from the reactor; the condensate was collected in a suitable receiver. The pyridine and "the picolines were isolated from the condensate by; fractional distillation. The

pyridine content of the reaction product was about 20.9%

The 3-picoline amounted to about it was about 95%pure.. Y Examplell" The process of Example 10 was, repeated with the exception that the catalyst used was a silica-magnesia catalyst impregnated with 10% "zinc fluoride. 'The pyridine in the reaction product amounted: to 19%. The yield of reaction product was about 0.50 to 0.60 pound per pound of acetylene passed through the reactor.

Exa'mplelZ t Y- A zinc Filtrol catalyst was prepared as follows: 2,500 grams of Filtrol 58 (which is a grade of montmorillonite clay having an amorphous or gel structure) was placed in a five-gallon glass container and a zinc chloride solution (227 grams of anhydrous zinc chloride was dissolved in 17 pounds of distilled water) was poured over the Filtrol. After this solution was poured over the Filtrol, a slurry was made by stirring for about one hour. The solids were removed from the slurry by filtration. The residue was removed from the filter and returned to the glass container. It was treated again with a zinc chloride solution prepared as mentioned above. The resulting slurry was filtered again. This process ofslurrying the Filtrol and removing the aqueous solution was repeated fifteen times. Finally, the zinc Filtrol was thoroughly washed with distilled water. It was then dried in an oven and ground. Analyses of the thus-prepared catalyst showed it to contain about 2.5% zinc.

The process of Example 10 was repeated with the exception that the above prepared zinc Filtrol was used as catalyst. The condensate obtained was subjected to.fractional distillation through an eflicient fractionating column to recover pyridine and S-picoline. The pyridine recovered amounted to about 7.9%. The 3-picoline recovered amounted to about 11%; as recovered from the fractionating column, the purity of the 3-picoline was more than 95 Example 13 The process of Example 9 was repeated with the exception that the catalyst used was alumina impregnated with 10% cupric chloride. The pyridine content of the condensate was about 14.8%. The condensate amounted to about 0.35 to 0.40 pound per pound of acetylene used.

Example 14 Instead of using acetylene, we can use the hydratedform of acetylene, i. e., acetaldehyde. We prepared a gaseous mixture of one mole of acetaldehyde, one mole of ammonia, and two moles of methanol. This mixture was reacted as was the mixture used in Example 4. The yields of pyridine, Zi-picoline, and of 2-picoline were as In place of the activated alumina, the silica magnesia,

amount. 1

. The temperature at which the reaction is conducted thel Fi1tro1, .andthe zeolite asicatalyst supports, we may use other-catalyst supports, such as fullers earth, pumice, silica, andthelike. 1 f In place ofthe zinc fluoride, the cupric chloride, and the cadmium fluoride, we may utilize other catalysts, such, as zinc chloride, cadmium chromate, cadmium molybdenate, lead chromate, zinc phosphate, and the like. Asa matter of fact, we have caused acetylene, ammonia, and methanol toreact by passing the mixture of. the vapors over alumina itself; while the conversion to pyridine, 3-picoline,- and other pyridines was not'high, it was appreciable. H i v,

As is evident from the specific examples given above, the proportions of the reactants may be varied widely. It is important, .however, to have all three reactants present if pyridine is to be'formed in any appreciable may be varied widely. \In general, we prefer to have the reaction temperature above about 400 C. and below about 500 C. It has been ourexperience that at temperatures below about 400 C., we have too large a proportion of the reactants passing through without reacting. At. temperatures above about 500 C., we, find that our catalyst becomes inactivated more rapidly and we obtaintoo many side reactions.

3 Weclaim asour invention:.

1. The-process of preparing pyridine and 3-picoline which comprises an interactionof acetylene, ammonia, -and .1nethanol in the presence of a catalyst useful in the aration of picolines from acetylene and ammonia maintained at a temperature between about 400 C. to about 500 C. and recovering pyridine and 3-picoline from the reaction product.

4. The process of preparing pyridine and 3-picoline which comprises mixing the vapors of acetylene, ammonia, and methanol, passing the resultant mixture through a reactor containing a catalyst comprising zinc fluoride maintained at a temperature between about 400 C. to about 500 C., and recovering pyridine and 3- picoline from the reaction product.

5. The process of preparing pyridine which comprises mixing the vapors of acetylene, ammonia, and methanol, passing the resultant mixture through a reactor containing a catalyst comprising an activated alumina impregnated with zinc fluoride maintained at a temperature between about 400 C. and about 500 C. and recovering pyridine from the reaction product.

6. The process of preparing pyridine which comprises mixing the vapors of acetylene, ammonia, and methanol, passing the resultant mixture through a reactor contain ing a catalyst comprising activated alumina impregnated with 10% zinc fluoride maintained at a temperature bebetween about 400 C. and about 500 C. and recovering pyridine from the reaction product.

7. The process of preparing pyridine which comprises mixing the vapors of acetylene, ammonia, and methanol, passing the resultant mixture through a reactor containing a catalyst comprising activated alumina impregnated with 10% zinc fluoride maintained at a temperature between about 470 C. and 480 C., and recovering pyridine from the reaction product.

8. The process of preparing pyridine which comprises mixing the vapors of acetylene, ammonia, and methanol, passing the resultant mixture through a reactor contain ing a catalyst comprising activatedalumina impregnated with 1.0% zinofluoride maintained at a 'temperature'between abont'41'5' .C. and 425 C., and recovering pyridine from vthe'reaction product. v

'9, The process of preparing pyridine which comprises preparing a gaseous mixture composed of about two parts of acetylene, of about .four and one-half parts of arm monia, and of about one part of methanol, passing the resultant mixture through a reactor containing a catalyst comprising activated alumina impregnated with 10% zinc fluoride maintained at a temperature between about 470 C. and 480 C., and recovering pyridine from the reaction product. v

10. The process of preparing pyridine which comprises preparing a gaseous mixture composed of about two parts of acetylene, of about four and one-half parts of ammonia, and of about one part of methanol, passing the resultant mixture through a reactor containing a catalyst comprising activated alumina impregnated With zinc fluoride maintained at a temperature between about 415 C. and 425 C. and recovering pyridine from the reaction product.

11. The process of preparing pyridine and 3-picoline which comprises preparing a gaseous mixture composed of acetylene, ammonia, and methanol in a ratio of one mole of acetylene to one mole of ammonia to one mole of methanol passing the resultant mixture through a reactor containing a catalyst useful in the preparation of picolines from acetylene and ammonia maintained at an elevated temperaturqand recovering pyridine and 3-picoline from "the reaction product. V

12*. The process of "claim 3 in which the gaseous miitf ture is composed of acetylene, ammonia, and methanol in molar ratios of 1:1:1.

1 13. The processofclaim 3 inwhichthe gaseous mixture iscompo'sed of acetylene ammonia, and methanol in molar ratios iof 1:1:3.

I .314. The process/of preparing pyridine and 3-picoline which comprises {mixingthe vapors of ,acetaldehyde (hydrated acetylene), ammonia, and methanol, passing the resultant mixture through a reactor containing a cat'- alyst useful in the preparation of picolines from acetylene and ammonia maintained at an elevated temperature, and

recovering pyridine and .3-picoline from the reaction product. a

References Cited the file of this patent UNITED STATES PATENTS 1,799,722 Arno1d Apr. 7', i931 1,875,746 "Martin Sept. 6, 193:;

1,882,518 NiCOdCmUS Oct. 11, 1932 2,700,042 Aries Jan. 18, 1955 FOREIGN PATENTS 332,623 Great Britain -v 1929 Germany Sept. 27, 1928 516,765 v I OTHER REFERENCES Ishiguro et a. Chem. AbsL, vol. 47, C01. 6416 1953' citing J. Pharm. Soc., Japanof 1952. 

1. THE PROCESS OF PREPARING PYRIDINE AND 3-PICOLINE WHICH COMPRISES AN INTERACTION OF ACETYLENE, AMMONIA, AND METHANOL IN THE PRESENCE OF A CATALYST USEFUL IN THE PREPARATION OF PICOLINES FROM ACETYLENE AND AMMONIA. 